Fix: do not fail TaskRun for concurrent modification errors

This commit fixes the behaviour that a concurrent modification error
when stopping sidecar will fail the TaskRun, which could cause
successful Tasks to fail even though it could succeed after retrying.

/kind bug

pkg/reconciler/taskrun/taskrun.go

@@ -280,6 +280,12 @@ func (c *Reconciler) stopSidecars(ctx context.Context, tr *v1.TaskRun) error {
 		// it has probably evicted. We can return the error, but we consider it a permanent one.
 		return controller.NewPermanentError(err)
 	} else if err != nil {
+		// It is admissible for Pods to fail with concurrentModification errors
+		// when stopping sideCars. Instead of failing the TaskRun, we shall just
+		// let the reconciler requeue.
+		if isConcurrentModificationError(err) {
+			return controller.NewRequeueAfter(time.Second)
+		}
 		logger.Errorf("Error stopping sidecars for TaskRun %q: %v", tr.Name, err)
 		tr.Status.MarkResourceFailed(v1.TaskRunReasonStopSidecarFailed, err)
 	}
@@ -1014,6 +1020,28 @@ func isResourceQuotaConflictError(err error) bool {
 	return k8ErrStatus.Details != nil && k8ErrStatus.Details.Kind == "resourcequotas"
 }
 
+const (
+	// TODO(#7466) Currently this appears as a local constant due to upstream dependencies bump blocker.
+	// This shall reference to k8s.io/apiserver/pkg/registry/generic/registry.OptimisticLockErrorMsg
+	// once #7464 is unblocked.
+	optimisticLockErrorMsg = "the object has been modified; please apply your changes to the latest version and try again"
+)
+
+// isConcurrentModificationError determines whether it is a concurrent
+// modification  error depending on its error type and error message.
+func isConcurrentModificationError(err error) bool {
+	if !k8serrors.IsConflict(err) {
+		return false
+	}
+
+	var se *k8serrors.StatusError
+	if !errors.As(err, &se) {
+		return false
+	}
+
+	return strings.Contains(err.Error(), optimisticLockErrorMsg)
+}
+
 // retryTaskRun archives taskRun.Status to taskRun.Status.RetriesStatus, and set
 // taskRun status to Unknown with Reason v1.TaskRunReasonToBeRetried.
 func retryTaskRun(tr *v1.TaskRun, message string) {

pkg/reconciler/taskrun/taskrun_test.go

@@ -65,6 +65,7 @@ import (
 	corev1 "k8s.io/api/core/v1"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	k8sapierrors "k8s.io/apimachinery/pkg/api/errors"
+	k8serrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -6282,6 +6283,33 @@ status:
 	}
 }
 
+func TestIsConcurrentModificationError(t *testing.T) {
+	tcs := []struct {
+		description string
+		err         error
+		want        bool
+	}{{
+		description: "conflict error not concurrent modification",
+		err:         k8serrors.NewConflict(schema.ParseGroupResource("foo"), "bar", errors.New("not concurrent modification")),
+		want:        false,
+	}, {
+		description: "concurrent modification error",
+		err:         k8serrors.NewConflict(schema.ParseGroupResource("foo"), "bar", errors.New(optimisticLockErrorMsg)),
+		want:        true,
+	}, {
+		description: "not conflict error",
+		err:         k8serrors.NewNotFound(schema.ParseGroupResource("foo"), "bar"),
+		want:        false,
+	}}
+	for _, tc := range tcs {
+		t.Run(tc.description, func(t *testing.T) {
+			if isConcurrentModificationError(tc.err) != tc.want {
+				t.Errorf("Unexpected concurrent modification error state")
+			}
+		})
+	}
+}
+
 // getResolvedResolutionRequest is a helper function to return the ResolutionRequest and the data is filled with resourceBytes,
 // the ResolutionRequest's name is generated by resolverName, namespace and runName.
 func getResolvedResolutionRequest(t *testing.T, resolverName string, resourceBytes []byte, namespace string, runName string) resolutionv1beta1.ResolutionRequest {